This invention relates to the production of sodium phenol sulfonate. More particularly it relates to a process for preparing substantially anhydrous sodium phenol sulfonate.
Sodium phenol sulfonate is a valuable intermediate employed in the manufacture of alkanoyloxybenzene sulfonates. Sodium alkanoloxybenzene sulfonates are disclosed as being useful in a toilet bar in U.S. Pat. No. 3,503,888 issued Mar. 31, 1970 to R. O. Miller, et al. The preparation of sodium alkanoyloxybenzene sulfonates are generally performed by the reaction of an alkanoyloxychloride with sodium phenol sulfonate. One method of preparation wherein the above-mentioned reactants are brought together in the presence of an organic solvent such as dimethyl formamide is taught by F. Puschel and O. Todorov, Tenside 7 (1970) 249-54, 252. Another method for preparing alkanoyloxybenzene sulfonates is disclosed in EPO publication 148,148 wherein substantially solid anhydrous sodium phenol sulfonate is reacted with an alkanoyloxyhalide at a temperature in the range of about 90.degree. C. to about 200.degree. C. in the substantial absence of a solvent or inert reaction medium.
Alkanoyloxybenzene sulfonates, and particularly the sodium derivative, are utilized in detergent materials wherein the color of the material is important to commercial utility. It is preferred that the material be colorless or to have as little color as possible such as 50 APHA or below based upon a 10% dry weight solution. However, in the preparation of sodium phenol sulfonates to provide substantially anhydrous material, it has been found unexpectedly that drying the commonly available dihydrate crystals does not occur below about two percent water level without excessive heating resulting in discoloration of the product and some degradation which forms undesirable by-products.
There is needed an efficient and facile process for the manufacture of substantially anhydrous sodium phenol sulfonate having acceptable color for detergent utility.